Passive seat belt systems are becoming increasingly popular in vehicles. In a passive system, the seat belt is automatically positioned around the vehicle occupant as the occupant enters the vehicle and closes the door. The popularity of the passive system arises from the fact that it is self-deploying upon entry to and exit from the vehicle.
Passive systems are of typically two configurations. In one configuration, the seat belt is mounted by means of a seat belt retractor to the floor of the vehicle. The seat belt passes over the upper torso of the occupant to an anchor point on the vehicle door. The other configuration typically used in vehicles retractably mounts the seat belt to the door of the vehicle and has the anchor point on the vehicle floor. The retractor is an integral part of any passive system. The retractor protracts or extends the seat belt as the door is opened upon entry into or exit from the vehicle. Likewise, when the door of the vehicle is closed with the occupant seated the retractor removes the slack from the belt, thereby automatically positioning the belt to restrain the vehicle occupant in the event of an emergency stop or accident.
The passive systems found in the prior art are not without limitations, however. For example, in an effort to allow repair or maintenance activities to be performed on the interior of the vehicle, and to allow the occupant a choice of whether or not to use the passive system, the seat belts in some passive systems have been releasably attached to the anchor point. A typical arrangement places a seat belt buckle on the end of the belt and a tongue member on the anchor point. In the normal mode of operation the buckle on the belt would be connected to the tongue member. However, if the occupant wishes, for some reason, to break the connection between the seat belt and the anchor point, the buckle is released and the seat belt winds back into the retractor. All too often, the seat belt is never reconnected to the door. That is, this type of passive system lends itself to easy defeating by the occupant.
In an effort to prevent the defeating of the passive system by the occupant, certain other types of passive systems permanently attach the end of the seat belt to the anchor point. In these types of systems, the seat belt cannot be released at the anchor point or at the retractor. This system, however, also has certain limitations. The first of these is that in an accident situation where the door is damaged to the extent that it will not open, the seat belt may possibly hamper removal of the vehicle occupant.
Another limitation involves the effect of the seat belt retractor mechanism. The types of seat belt retractors commonly utilized in passive systems include inertia sensing mechanisms which lock the seat belt against protraction in emergency situations. The inertia sensing mechanism performs its function by sensing the rapidity of movement of the vehicle and/or of the occupant, and locks the belt upon sharp deceleration of one or both. A possibility exists, if the retractor becomes damaged in an accident situation, that the removal of the belt from the occupant can be hampered by the resulting inability to protract the belt. A possibility also exists, if the vehicle ends up upside down or on its side, that the weight of the occupant against the belt will impede the disengaging of the inertia sensing mechanism, thereby also hampering exit from the vehicle.
The passive systems found in the prior art do not provide a satisfactory solution to the problem of designing a passive system which cannot be defeated by the occupant, and yet allows a rapid exit from the vehicle in an emergency situation. Accordingly, it is the principal object of this invention to improve the design of passive seat belt systems having the seat belt permanently attached to the door.
It is another object of this invention to improve the safety of passive seat belt systems.
It is another object of this invention to allow the occupant of a vehicle employing a passive system to quickly exit the vehicle in an accident situation.
It is a final object of this invention to release the tension of a passive seat belt in an accident situation in which such releasing would not otherwise be possible.